Stereochemical relay through oligoureas

1. Stereochemical relay through oligoureas 11/11/2004 P M - Is it possible to control the orientation of the helix with a chiral group A? - Is it possible to control a stereoselective reaction on B ?

2. Synthesis

3. Synthesis

4. Synthesis

5. Synthesis

6. Synthesis Symmetrical oligoureas

7. Synthesis Symmetrical oligoureas

8. Synthesis

9. Conformation of the ureas Conformation in solution (CDCl3) and in the single cristal (Et) 5.81 ppm (i-Pr) 5.88 ppm 5.65 ppm ≈ 10 Å Two conformations at low temperature R = Et 2 conformers 50/50 à -60°C R = i-Pr 2 conformers 55/45 à -30°C

10. With an asymmetric centre (s-Bu, racemic) 5.96 ppm M P Conformation of the ureas Conformation in solution (CDCl3) and in the single cristal Two enantiomer helices Each imposes a different conformation of a same enantiomer of the s-Bu

11. 6.00 ppm 5.91 ppm 6.00 ppm symmetrical octaurea Conformation of the ureas Conformation in solution (CDCl3) of the oligoureas 5.91 ppm 5.91 ppm 6.03 ppm 6.02 ppm Symmetrical tetraurea unsymmetrical tetraurea

12. Conformation of the ureas Conformation in solution (CDCl3) of the oligoureas Chiral sulfoxide 6.01 ppm 5.93 ppm 6.05 ppm 5.92 ppm 6.03 ppm 6.04 ppm

13. ? ? A chiral i-propyl group as a sensor How to know if the sulfoxide controls the sense of the helix in solution ?

14. Chiral i-propyl as a sensor R = CD3 de = 65% R = 13CH3 de = 81% R = CD3 87% R = 13CH3 77% R = CD3 52% R = 13CH3 68% Dynamic Thermodynamic Resolution Thayumanavan, S.; Basu, A.; Beak P. J. Am. Chem. Soc.1997, 119, 8209-8216